CN110165272B

CN110165272B - Fuel cell stack

Info

Publication number: CN110165272B
Application number: CN201811591245.0A
Authority: CN
Inventors: 永长秀男
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2018-02-13
Filing date: 2018-12-25
Publication date: 2022-03-11
Anticipated expiration: 2038-12-25
Also published as: JP2019140004A; US11063287B2; EP3525277A1; EP3525277B1; JP6870630B2; US20190252711A1; CN110165272A

Abstract

The fuel cell stack includes: a stacked body including stacked unit cells; an end plate clamping the stacked body in a stacking direction in which the unit cells are stacked; a tension plate for fastening the end plate; fixing mechanisms for fixing the tension plate to the end plate, at least one of the fixing mechanisms including: a recess formed in an outer peripheral edge of one of the end plates; a bolt hole formed in one of the end plates, formed concentrically with the recess, and having an inner diameter smaller than that of the recess; a through hole formed in the tension plate; a sleeve formed in a cylindrical shape having a through hole and fitted into the through hole and the recess of the tension plate; and a bolt that passes through the through hole of the sleeve and is screwed into the bolt hole, the through hole of the tension plate includes a tapered inner peripheral surface whose inner diameter is gradually reduced toward one of the end plates in an axial direction of the bolt, the sleeve includes a tapered outer peripheral surface whose outer diameter is gradually reduced toward the one of the end plates in the axial direction, and the tapered outer peripheral surface is in contact with the tapered inner peripheral surface.

Description

Fuel cell stack

Technical Field

The present invention relates to a fuel cell stack.

Background

A fuel cell stack is known, which includes: a stacked body including stacked unit cells; and an end plate that sandwiches the stacked body from the stacking direction. In such a fuel cell stack, in view of reducing the contact resistance between the unit cells and ensuring the sealing property between the unit cells, a pair of end plates are preferably fastened by tension plates so that a desired pressure can be applied to the stack in the stacking direction. The tension plate is fixed to the end plate in the following manner. Bolt holes are formed in the outer peripheral edge of the end plate. Through holes are formed in the tension plate so as to be aligned with the bolt holes. The tension plate is fixed to the end plate by screwing bolts from the tension plate into the bolt holes through the through holes in a state where the through holes and the bolt holes are aligned with each other (see, for example, japanese unexamined patent application publication No. 2008-152942).

In order to suppress an increase in the size of the fuel cell stack, it is conceivable to make the tension plate thin. However, in the case where the tension sheet is thinned, the durability of the tension sheet may be deteriorated. Herein, for example, in the case where the fuel cell stack is mounted on a vehicle, a slip may occur between the seat surface of the bolt and the tension plate due to driving vibration or the like, so that a local load may be applied on the inner circumference of the through-hole of the tension plate from the shaft portion of the bolt. This may enlarge the through-hole. When the through-hole of the tension plate is enlarged, abnormal noise (rattling) may occur between the through-hole and the bolt, and the pressure applied to the stacked body in the stacking direction may be reduced.

Disclosure of Invention

An object of the present invention is to provide a fuel cell stack that suppresses a decrease in pressure applied to a stack in a stacking direction.

The above object is achieved by a fuel cell stack comprising: a stacked body including stacked unit cells; end plates that sandwich the stacked body in a stacking direction in which the unit cells are stacked; a tension plate which fastens the end plate; and a fixing mechanism that fixes the tension plate to the end plate, wherein at least one of the fixing mechanisms includes: a recess formed in an outer peripheral edge of one of the end plates; a bolt hole formed in the one of the end plates, formed concentrically with the depression, and having a smaller inner diameter than the depression; a through hole formed on the tension plate; a sleeve formed in a cylindrical shape having a through hole and fitted into the through hole and the recess of the tension plate; and a bolt that passes through the through hole of the sleeve and is screwed into the bolt hole, the through hole of the tension plate including a tapered inner peripheral surface whose inner diameter is gradually reduced toward the one of the end plates in an axial direction of the bolt, the sleeve including a tapered outer peripheral surface whose outer diameter is gradually reduced toward the one of the end plates in the axial direction, and the tapered outer peripheral surface being in contact with the tapered inner peripheral surface.

The tapered outer peripheral surface of the sleeve is in surface contact with the tapered inner peripheral surface of the through-hole of the tension plate, thereby ensuring a contact area between the two surfaces and bringing the two surfaces into close contact with each other. Therefore, local load concentration on the tapered inner peripheral surface of the through hole of the tension plate can be suppressed, and enlargement of the through hole of the tension plate can be suppressed. Therefore, the occurrence of abnormal noise between the sleeve and the tension plate is suppressed, and the decrease in the pressure applied to the stacked body in the stacking direction is suppressed.

The recessed portion may include a cylindrical inner peripheral surface whose inner diameter is constant in the axial direction, the sleeve may include a cylindrical outer peripheral surface whose outer diameter is constant in the axial direction from the tapered outer peripheral surface, and the cylindrical inner peripheral surface may be fitted with the cylindrical outer peripheral surface.

There may be formed a chamfered portion at an opening edge of the recess portion to avoid contact with the tapered outer peripheral surface.

The depth of the recess in the axial direction may be greater than the length of the cylindrical outer peripheral surface of the sleeve in the axial direction.

The inner diameter of the through hole of the sleeve may be larger than the outer diameter of the shaft portion of the bolt passing through the through hole of the sleeve by a predetermined amount.

The invention has the advantages of

According to the invention, it is possible to provide a fuel cell stack that suppresses a decrease in pressure applied to the stack in the stacking direction.

Drawings

Fig. 1 is a perspective view of a fuel cell stack according to the present embodiment;

FIG. 2 is an enlarged view of a portion of FIG. 1;

fig. 3 is a sectional view showing the periphery of the fixing mechanism that fixes the tension plate to the end plate;

FIG. 4A is a partial enlarged view of FIG. 3, and FIG. 4B is an enlarged view of the sleeve deeply inserted into the recess; and

fig. 5 is a view showing a section of the periphery of the fixing mechanism according to the modification.

Detailed Description

Fig. 1 is a perspective view of a fuel cell stack 1 (hereinafter referred to as a stack 1) according to the present embodiment. The stack 1 comprises a stack 12,

end plates

14a and 14b, tension plates 24 and a fixing mechanism 30. The stack 12 includes stacked unit cells 11,

terminal plates

13a and 13b disposed at respective ends of the unit cells 11, and a pressing plate 13c disposed between the terminal plate 13a and the end plate 14 a. Fig. 1 shows the stacking direction LD in which the unit cells 11 and the like are stacked. The unit cell 11 is a polymer electrolyte fuel cell that generates electric power by being supplied with a fuel gas (e.g., hydrogen gas) and an oxidant gas (e.g., air) as reaction gases. The

terminal plates

13a and 13b are arranged to sandwich the unit cells 11. In the present embodiment, each of the

terminal plates

13a and 13b has a terminal portion for extracting the generated electric power from the stack 1 to the outside and protruding to the outside of the stack 12.

The

end plates

14a and 14b sandwich the stack 12 in the stacking direction LD, and the

end plates

14a and 14b are fastened by the tension plate 24 so as to apply a desired pressure to the stack 12 in the stacking direction LD. This ensures a reduction in contact resistance between the unit cells 11 and ensures sealing characteristics between the unit cells 11. Each of the

end plates

14a and 14b is made of, for example, metal. The end plate 14b includes a portion protruding from the stack 12 in a direction perpendicular to the stacking direction LD. For example, in the case where the stack 1 is mounted on a vehicle, the end plate 14b is fixed to a member constituting the vehicle body. The end plate 14b is provided with supply ports for supplying the fuel gas, the oxidant gas, and the cooling water to the unit cells 11, and discharge ports for discharging them.

A tension plate 24 facing the outer peripheral surface of the stack body 12 extends in the stacking direction LD and fastens the

end plates

14a and 14 b. Specifically, the tension plates 24 are fixed to the outer peripheral edges 14a1 and 14b1 of the

respective end plates

14a and 14b so that a desired pressure in the stacking direction LD is applied to the stacked body 12 through the

end plates

14a and 14 b. The tension plate 24 is made of metal. A tension plate 24 is disposed around the stack 12. The tension plate 24 is formed to be thin compared with its longitudinal length and its width in a short direction perpendicular to the longitudinal direction. This suppresses an increase in the size of the stack 1, specifically, an increase in the size of the stack 1 in the plane direction perpendicular to the stacking direction LD. The fixing mechanism 30 is a mechanism for fixing the tension plate 24 to the

end plates

14a and 14 b. The fixing mechanism 30 will be described later.

The pressing plate 13c disposed between the end plate 14a and the terminal plate 13a is pressed by the end of the adjusting screw 14c attached to the end plate 14 a. Specifically, by adjusting the screwing amount of the adjustment screw 14c into the screw hole formed in the end plate 14a, the protruding amount of the adjustment screw 14c from the end plate 14a toward the pressure plate 13c is adjusted. Therefore, the pressure applied to the stacking direction LD of the stack body 12 is finely adjusted. In addition, each insulator, not shown, for ensuring insulation is provided between the terminal plate 13a and the presser plate 13c and between the terminal plate 13b and the end plate 14 b.

Next, the fixing mechanism 30 will be described. One end of the tension plate 24 is fixed to the end plate 14a by two fixing mechanisms 30, and the other end of the tension plate 24 is also fixed to the end plate 14b by two fixing mechanisms 30. Fig. 2 is a partially enlarged view of fig. 1. The fixing mechanism 30 includes a bolt 40, a sleeve 50 through which the bolt 40 passes, a through hole 25 formed in the tension plate 24, and the like. As will be described in detail later, the bolts 40 are screwed into bolt holes formed in the end plate 14a to fix the sleeves 50 to the end plate 14a by the bolts 40, and to fix the tension plate 24 to the end plate 14a by the sleeves 50. The bolt 40 fixes the sleeve 50 to the end plate 14a in a posture in which the axial direction AD of the bolt 40 is perpendicular to the stacking direction LD.

Fig. 3 is a sectional view showing the periphery of the fixing mechanism 30 that fixes the tension plate 24 to the end plate 14 a. Although not shown in fig. 2, as shown in fig. 3, a recess 15 is formed on the outer peripheral edge 14a1 of the end plate 14 a. The recess 15 has a circular shape when viewed in the axial direction AD of the bolt 40. Specifically, the recessed portion 15 includes a cylindrical inner peripheral surface 17 and a bottom surface 18. Bolt holes 19 are formed in the end plate 14 a. The bolt hole 19 formed concentrically with the recess 15 has an inner diameter smaller than that of the recess 15. An inner peripheral surface of the bolt hole 19 is formed with a thread groove to be screwed with a shaft portion 46 of a bolt 40 described later. In addition, the fixing mechanism 30 includes not only the bolt 40 and the sleeve 50 but also the recess 15 and the bolt hole 19 formed in the end plate 14 a.

The through hole 25 of the tension plate 24 includes a tapered inner peripheral surface 25a, and the inner diameter of the tapered inner peripheral surface 25a gradually decreases toward the end plate 14a in the axial direction AD. The minimum inner diameter of the tapered inner peripheral surface 25a is substantially equal to or larger than the inner diameter of the cylindrical inner peripheral surface 17 of the recessed portion 15 of the end plate 14 a. In addition, the fixing mechanism 30 further includes a through hole 25 of the tension plate 24. The through-hole 25 will be described in detail later.

The bolt 40 made of metal includes a head portion 42, a seat surface 44, and a shaft portion 46. The shaft portion 46 is screwed into the bolt hole 19 of the end plate 14 a. The outer diameter of the seating surface 44 is greater than the respective outer diameters of the head portion 42 and the shaft portion 46. A shaft portion 46 formed with a thread on its outer peripheral surface is screwed into a thread groove of the bolt hole 19.

A sleeve 50 made of metal and formed into a substantially cylindrical shape is fitted into the through hole 25 of the tension plate 24 and the recess 15 of the end plate 14 a. The sleeve 50 includes an upper surface 54, a tapered outer peripheral surface 55, a through bore 56, a cylindrical outer peripheral surface 57, and a bottom surface 58. The upper surface 54 in contact with the seat surface 44 of the bolt 40 is pressed toward the end plate 14 a. In addition, the outer diameter of the seat surface 44 of the bolt 40 is smaller than the outer diameter of the upper surface 54 so that the seat surface 44 does not protrude outside the sleeve 50. The shaft portion 46 of the bolt 40 passes through the through hole 56. Unlike the bolt hole 19, the through hole 56 is formed in a smooth cylindrical shape without forming a thread groove on an inner circumferential surface thereof. The outer diameter of the tapered outer peripheral surface 55 gradually decreases in the axial direction AD toward the end plate 14 a. On the other hand, the outer diameter of the cylindrical outer peripheral surface 57 is constant in the axial direction AD. The cylindrical outer peripheral surface 57 is close to the end plate 14a as compared with the tapered outer peripheral surface 55. The outer diameter of the cylindrical outer peripheral surface 57 is substantially equal to or less than the minimum of the outer diameters of the tapered outer peripheral surfaces 55. The tapered outer peripheral surface 55 is in contact with the tapered inner peripheral surface 25a of the through hole 25 of the tension plate 24. The cylindrical outer peripheral surface 57 is in contact with the cylindrical inner peripheral surface 17 of the recess 15.

As described above, the shaft portion 46 of the bolt 40 is screwed into the bolt hole 19 through the through hole 56 in a state where the sleeve 50 is fitted into the through hole 25 of the tension plate 24 and the recess 15 of the end plate 14 a. Thus, the sleeve 50 is fixed to the end plate 14 a. As described above, the respective diameters of the tapered inner peripheral surface 25a of the through-hole 25 and the tapered outer peripheral surface 55 of the sleeve 50 gradually decrease toward the end plate 14a in the axial direction AD, in other words, the respective diameters gradually increase away from the end plate 14a in the axial direction AD. Therefore, in a state where the sleeve 50 is fitted into the through hole 25 of the tension plate 24 fixed to the end plate 14a, the tension plate 24 is restrained from separating from the sleeve 50 away from the end plate 14 a. That is, the fastening force between the end plate 14a and the bolt 40 is exerted on the sleeve 50, and the force exerted on the sleeve 50 is exerted on the tension plate 24, thereby fixing the tension plate 24 to the end plate 14 a. The same applies to the fixing mechanism 30 that fixes the other tension plates 24 to the end plate 14 b.

The tapered inner peripheral surface 25a of the through hole 25 and the tapered outer peripheral surface 55 of the sleeve 50, each formed in a tapered shape having substantially the same gradient, are in surface contact with each other. Therefore, it is ensured that the contact area between the tapered inner peripheral surface 25a and the tapered outer peripheral surface 55 is maintained in a close contact state. Since these two surfaces are in close contact with each other in this way, the load applied from the tapered outer peripheral surface 55 to the tapered inner peripheral surface 25a is dispersed, thereby suppressing local load concentration on the tapered inner peripheral surface 25 a. This suppresses the enlargement of the through-hole 25. For example, even when vibration of the vehicle equipped with the stack 1 is transmitted thereto, since the tapered inner peripheral surface 25a is in close contact with the tapered outer peripheral surface 55, enlargement of the through-hole 25 is suppressed. Therefore, a decrease in the pressure applied to the stack body 12 in the stacking direction LD is suppressed.

For example, it is assumed that the inner peripheral surface of the through hole of the tension plate whose inner diameter is constant in the axial direction is in contact with the outer peripheral surface of the sleeve whose outer diameter is constant in the axial direction. In this case, it may be difficult to bring the inner peripheral surface of the through hole of the tension plate and the outer peripheral surface of the sleeve into uniform contact with each other due to a dimensional error, an assembly error, or the like caused by machining accuracy. Therefore, it may be difficult to stably secure a contact area between the two surfaces. Therefore, stress may concentrate on a part of the inner circumferential surface of the through hole of the tension plate, which may enlarge the through hole of the tension plate. In particular, when the tension plate 24 is thin as in the present embodiment, such a problem is likely to occur. In the present embodiment, as described above, the tapered inner peripheral surface 25a and the tapered outer peripheral surface 55 are tapered and close to each other and are in surface contact, so that the enlargement of the through-hole 25 is suppressed.

Further, as described above, no thread groove is formed in the through hole 56 of the sleeve 50, and the inner diameter of the through hole 56 is larger than the outer diameter of the shaft portion 46 of the bolt 40 by a predetermined amount. Therefore, in a state where the bolt 40 is inserted into the through hole 56, the sleeve 50 can slightly move relative to the bolt 40. Since the sleeve 50 can slightly move relative to the bolt 40 in this way, it is possible to absorb dimensional errors and the like of each member and bring the tapered outer peripheral surface 55 of the sleeve 50 and the tapered inner peripheral surface 25a of the through-hole 25 into close contact with each other. Further, the difference between the inner diameter of the through hole 56 and the outer diameter of the shaft portion 46 of the bolt 40 may be set taking into consideration dimensional errors and the like of each member, and may be, for example, 0.5mm or more, 1.0mm or more, or 1.5mm or more.

In addition, the outer diameter of the cylindrical outer peripheral surface 57 is constant in the axial direction AD, and the inner diameter of the cylindrical inner peripheral surface 17 is also constant in the axial direction AD. For example, it is assumed that the cylindrical outer peripheral surface 57 and the cylindrical inner peripheral surface 17 are each formed in a tapered shape whose diameter gradually decreases toward the end plate 14a so as to be in surface contact with each other, as are the tapered outer peripheral surface 55 and the tapered inner peripheral surface 25 a. In this case, the recess 15 and the sleeve 50 may be excessively brought into close contact with each other, and it may be difficult to separate the sleeve 50 from the recess 15. Assume a case where the sleeve 50 is separated from the recess 15 in the following manner. For example, when several unit cells 11 need to be replaced in consideration of the test results of the completed stack 1, the stack 1 may be disassembled. In this case, if it is difficult to separate the sleeve 50 from the recessed portion 15, it may also be difficult to separate the tension plate 24 fixed to the end plate 14a by the sleeve 50, and thus the disassembling workability of the stack 1 may be deteriorated. In the present embodiment, since each diameter of the cylindrical outer peripheral surface 57 and the cylindrical inner peripheral surface 17 is constant in the axial direction AD, the recessed portion 15 and the sleeve 50 are suppressed from being excessively brought into close contact with each other, which suppresses deterioration of the disassembling workability.

Fig. 3 shows the depth L1 of the recess 15 and the length L5 of the cylindrical outer peripheral surface 57 of the sleeve 50. Depth L1 is greater than length L5. That is, the tension plate 24 is fixed to the end plate 14a with the bottom surface 58 of the sleeve 50 not in contact with the bottom surface 18 of the recess 15. For example, if the bottom surfaces 58 and 18 contact each other, the pressure applied from the bolt 40 to the sleeve 50 is dispersed not only to the tension plate 24 but also to the end plate 14 a. Therefore, the force applied from the sleeve 50 to the tension plate 24 may be reduced, and thus the tension plate 24 may not be fixed to the end plate 14a with sufficient force. Since the bottom surfaces 58 and 18 do not contact each other as described above in the present embodiment, the force applied from the bolt 40 to the sleeve 50 can be transmitted to the tension plate 24 without being dispersed to the end plate 14 a. Therefore, the tension plate 24 can be fixed to the end plate 14a with sufficient force.

Fig. 4A is a partially enlarged view of fig. 3. A chamfered portion 151 is formed around the opening edge of the recess 15 of the end plate 14 a. A groove portion 551 is formed between the tapered outer peripheral surface 55 and the cylindrical outer peripheral surface 57, and the groove portion 551 extends in the circumferential direction of the sleeve 50 and has an annual ring shape. The groove portion 551 is inevitably formed during the manufacturing process, and the sleeve 50 is not limited to having the depression portion 551.

Fig. 4B is an enlarged view of the sleeve 50 inserted deeply into the recess 15. Fig. 4B corresponds to fig. 4A. For example, the sleeve 50 may be inserted deeper into the recess 15 than intended due to dimensional errors of each member, or the like. Even in this case, the contact between the end plate 14a and the sleeve 50 is avoided by the chamfered portion 151. Even with this configuration, the force applied from the bolt 40 to the sleeve 50 can be transmitted to the tension plate 24 without being dispersed to the end plate 14a, and therefore the tension plate 24 can be fixed to the end plate 14a with sufficient force. In addition, since the chamfered portion 151 is formed, when the tension plate 24 is fixed to the end plate 14a, it is easy to insert the sleeve 50 into the recess 15, and the assembly workability of the stack 1 is also improved.

In the present embodiment, the tension plates 24 are fixed to the

end plates

14a and 14b by the fixing mechanism 30, but at least one tension plate may be fixed to at least one of the

end plates

14a and 14b by the fixing mechanism 30.

Next, a modification will be described. In this modification, the same components are denoted by the same reference numerals, and duplicate explanation is omitted. Fig. 5 is a view showing a section of the periphery of the fixing mechanism 30A according to the modification. Unlike the above-described embodiment, the sleeve 50A of the fixing mechanism 30A is not formed with the cylindrical outer peripheral surface 57, but has the tapered outer peripheral surface 55A in the entire axial direction. Further, unlike the above-described embodiment, the recessed portion 15A of the end plate 14aA is not formed with the cylindrical inner peripheral surface 17 having a constant inner diameter, but is formed with the tapered inner peripheral surface 17A having an inner diameter gradually decreasing toward the end plate 14 aA. As described above, the sleeve 50A is easier to manufacture than the sleeve 50 in the above embodiment, thereby suppressing an increase in manufacturing cost.

Although some embodiments of the present invention have been described in detail, the present invention is not limited to the specific embodiments, but may be changed or modified within the scope of the claimed invention.

Claims

1. A fuel cell stack comprising:

a stacked body including stacked unit cells;

end plates that sandwich the stacked body in a stacking direction in which the unit cells are stacked;

a tension plate fastening the end plate;

a fixing mechanism that fixes the tension plate to the end plate;

wherein,

at least one of the securing mechanisms comprises:

a recess formed in an outer peripheral edge of one of the end plates;

a bolt hole formed in the one of the end plates, formed concentrically with the recess, and having a smaller inner diameter than the recess;

a through hole formed on the tension plate;

a sleeve formed in a cylindrical shape having a through hole and fitted into the through hole and the recess of the tension plate; and

a bolt passing through the through hole of the sleeve and screwed into the bolt hole,

the through hole of the tension plate includes a tapered inner peripheral surface whose inner diameter is gradually reduced toward the one of the end plates in an axial direction of the bolt,

the sleeve includes a tapered outer peripheral surface whose outer diameter is gradually reduced toward the one of the end plates in the axial direction, and

the tapered outer peripheral surface is in contact with the tapered inner peripheral surface.

2. The fuel cell stack of claim 1,

the recessed portion includes a cylindrical inner peripheral surface whose inner diameter is constant in the axial direction,

the sleeve includes a cylindrical outer peripheral surface whose outer diameter is constant in the axial direction from the tapered outer peripheral surface, and

the cylindrical inner peripheral surface is fitted with the cylindrical outer peripheral surface.

3. The fuel cell stack according to claim 2, wherein a chamfered portion is formed at an opening edge of the recessed portion so as to avoid contact with the tapered outer peripheral surface.

4. A fuel cell stack according to claim 2 or 3, wherein a depth of said recess in said axial direction is larger than a length of said cylindrical outer peripheral surface of said sleeve in said axial direction.

5. The fuel cell stack according to any one of claims 1 to 3, wherein an inner diameter of the through hole of the sleeve is larger than an outer diameter of a shaft portion of the bolt passing through the through hole of the sleeve by a predetermined amount.

6. The fuel cell stack according to claim 4, wherein an inner diameter of the through hole of the sleeve is larger than an outer diameter of a shaft portion of the bolt passing through the through hole of the sleeve by a predetermined amount.